Composite electrical bus bar



Sept- 17, 1968 G. H. PARKER ETAL. 3,402,254

COMPOSTE ELECTRICA' BUS BAR Filed Dec. 2, 1966 W H. Pwzb,

W A. mam,

United States Patent O 3,402,254 COMPOSITE ELECTRICAL BUS BAR Gregory H. Parker, Winnetka, Ill., and Edwin A. Miller,

Attleboro, Mass., assignors to Texas Instruments Incorporated, Dallas, Tex., a corporation of Delaware Filed Dec. 2, 1966, Ser. No. 598,818 4 Claims. (Cl. 174-133) ABSTRACT OF THE DISCLOSURE A composite strip of relatively thick aluminum and relatively thin copper metallurgically bonded thereto is longitudinally folded by oppositely bending opposite marginal portions flatwise against intermediate portions so as to place the edges of the strip near one another, with a reverse bend of the intermediate portion formed therebetween. The small spaces between the edges and the reverse bend are infilled with a protective material. The result is a bus bar having rounded longitudinal edges with opposite copper faces along one side and opposite aluminum faces along the other side. In another form one margin only of the composite is marginally bent with its edge substantially spaced from the edge of edge of the unfolded margin. The result is a bus bar having a rounded longitudinal edge along one side which has opposite copper faces and having opposite copper and aluminum faces along the other side.

This invention relates to composite electrical conductors and more particularly to such conductors constituting bus bars and the like.

Among the several objects of the invention may be noted the provision of a low-cost, strong, light-weight and highly conductive bus bar marginally shaped to facilitate application thereto of spring-clip connectors; and the provi-sion of a bus bar of the class described which is useful to form a conductive transition member between copper and aluminum electrical networks. Other objects and features will be in the part apparent and in part pointed out hereinafter.

The invention accordingly comprises the methods and products hereinafter described, the scope of the invention being indicated in the following claims.

In the accompanying drawings, in which several of various possible embodiments of the invention are illustrated,

FIG. 1 is a fragmentary view illustrating one form of the invention; and

FIG. 2 is a fragmentary view showing another form of the invention.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Bus bars for carrying substantial currents have heretofore been composed of substantially heavy copper bars of rectangular cross sections having comparatively sharp angular corners. The weight of copper employed made them expensive and the angular corners were not ideal for the reception of the connecting clips. Morever, such solid bars were not ideal for use as transition members between copper and aluminum networks because of electrolytic corrosion problems encountered in making aluminum-to-copper connections.

Referring now more particularly to FIG. 1, it shows what was Originally a flat composite sheet constituted by a comparatively thick layer of aluminum 1 to which has been interfacially 'metallurgically bonded on one side a comparatively thin copper layer 3. Such a composite is sometimes referred to as single-clad plate. A ratio of thickness of the aluminum 1 to the copper 3 may, for example, be nine to one, and the total thickness of the starting plate ICC may be 1A inch. The starting plate is preferably in strip form and wide enough to admit of opposite marginal bending at 180 turns to make a narrower thicker strip (FIG. 1). This constitutes a finished bus bar made according to the invention.

The original strip is marginally bent over in one direction as shown at numeral 5 so as to place the copper layer 3 on the outside. The original strip is also marginally bent over in the opposite direction as shown at bend 7 to place the aluminum layer 1 on the outside. The bentovcr parts are numbered 2 and 4. The original composite is also reversely bent as shown at reverse bend 9. This bend 9 is parallel to the bends 5 and 7 and lies therebetween. Its position is preferably midway between bends 5 and 7 but not necessarily so. The reverse double bent portion 9 has the effect of placing all parts of opposite faces of the resulting bus bar in the same plane, with the exception of narrow slot 11 on each side. These slots may be infilled with a suitable solder or other protective material, which is shown by stippling.

The above-described form of the invention (FIG. l) has various advantages, an important one of which is the fact that comparatively thin single-clad composite starting plate may be used as starting material to produce a comparatively thick bus bar. The total thickness of this composite starting plate is on the order of one-half the thickness of the finally constructed bus bar. Of this thickness the larger amount is provided by the aluminum, which is highly conductive but less costly than copper and makes the bus bar of lighter weight. For example, the starting plate may be 1A; inch thick, resulting in a 1A inch thick bus bar. Another advantage is that the opposite faces on one side of the finished bus bar are constituted by copper and the opposite faces on the other side are constituted by aluminum. Thus, when transition joints are to be made between copper and aluminum networks, the former are connected to the side of the bus bar having exposed copper and the latter are connected to the side having exposed surfaces of aluminum` This avoids the occurrence of any electrolytic corrosion at any contacting but unbonded copper-to-aluminum joints. Another advantage is that, by bending the starting strip as above described, the sidewise edges of the bus bar become smoothly rounded as shown at the bends 5 and 7. Thus, connecting spring-contact clips can more readily be transversely applied to the bar with less wear and tear than heretofore.

In FIG. 2 is shown another form of the invention in which a fiat starting composite strip has copper and alu- 'minum layers 13 and 15, respectively. In this case the original strip is longit'udinally bent only once, as shown at 17. The folded-over portion is narrower than the remainder, their edges being out of register. This produces a bus bar which has a form on one side wherein the copper is on the outside, which is like the form on the left side of the bus bar of FIG. 1. The right side of the FIG. 2 construction has copper only on one (bottom) side and aluminum on the other (top) side. When this form of the finished bus bar is employed as a transition joint between copper and aluminum electrical networks, the copper connections can be made on the left side by transversely applied copper clips. The aluminum connections are made on the top only of the right side of the bar, as by welding, bolting or the like.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawin'gs shall be interpreted as illustrative and not in a limiting sense.

What is clairned is:

1. An electrical bus bar comprising a composite sheet composed of an aluminum layer clad with a copper layer, said sheet having one marginal portion bent with a 180- smoothly rounded turn against another portion of the sheet with the aluminum layer inside, the margins of the folded portions being out of register so as to provide along one side of the bus bar opposite copper facings and along the other side of the bus bar opposite aluminum and copper facings.

'2. An electrical bus bar comprising a composite bonded strip having bonded layers of different comparatively thick and thin metals, said strip having oppositely bent portions forming smoothly rounded marginal turns, one of said portions and a part of the remainder of the strip forming interfacially engaged face portions of one of the metal layers, another of said portions and a part of the remainder of the strip forming interfacially engaged face portions of the other metal layer, whereby face areas on opposite faces on one longitudinal side of the bus bar present faces of one metal and opposite faces on the other longitudinal side of the bar present faces of the other metal.

3. An electrical bus bar comprising a composite bonded metal strip having bonded layers of comparatively thick aluminum and comparatively thin copper, said strip having oppositely bent portions :forming smoothly rounded marginal turns, one of said portions and a part of the remainder of the strip formin'g nterfacially engaged face portions of the aluminum layer, another of said portions and a part of the remainder of the strip forming interfacially engaged face portions of the copper layer, whereby face areas on opposite longitudinal faces on one side of the bus bar present copper faces and opposite faces on the other longitudinal side of the bar present aluminum faces.

4. An electrical bus bar according to claim 3, including a doubly bent portion between the two areas of interfacial engagement which places all surfaces in each opposite side of the bar in substantially the same plane.

References Cited UNITED STATES PATENTS 1,801,110 4/1931 Ruder 72-700X 2,752,667 7/ 1956- Schaefer 29-197 FOREIGN PATENTS 914,139 7/ 1954 Germany.

25 LEWIS H. MYERS, Primary Examiner.

E. GOLDBERG, Assistant Examner. 

